During the operation of navigation devices in vehicles, the algorithm for calculating a route is triggered at the start of a journey by the respective user if it is necessary to determine the route to be travelled to the respective destination. Furthermore, the respective algorithm for calculating a route is also triggered when specific events occur, by way of example when messages regarding traffic obstructions or accident reports are received by radio. Such events or messages then lead to the optimal route being recalculated.
In addition, cloud-based solutions are known in which the time of day, the volume of traffic expected on specific stretches of road and also experience (for example traffic jams during school holidays) are taken into account.
In the above mentioned cases, the route is calculated in each case on the basis of specific trigger signals of the user or based on messages or events. As a consequence, the flexibility of the algorithms for calculating a route is limited, wherein in particular a recalculation is often delayed as a consequence of being dependent upon specific trigger signals or messages.
EP 2 201 552 B1 discloses inter alia a navigation system and a method for calculating and outputting an alternative road route in the case of warnings of traffic disruption, wherein at least one alternative road route is determined that is not affected by traffic jams and leads to rejoining an original road route.
With regard to further prior art, reference is made merely by way of example to JP 2008241507 A, JP 2001033265 A, WO 2006/070583 A1 and U.S. Pat. No. 7,818,125 B2.